We know that Khushi has said yes to marrying Shyam. I think Buaji will hurry the engagement and the wedding fearing that she may change her mind. Shyam too will try to impress upon her to do so both directly and indirectly. He may also ask the Guptas to keep it a low key affair given Shashi's health considerations. He may even explicitly state that the Raizadas should not be invited as they are too rich to attend weddings of simple folk like them. Since Khushi is desperately trying to heal herself from the hurt inflicted by Arnav, she may agree.
In the mean time, Arnav will be increasing unhappy at the Raizada house but may not admit it to the rest of the family. La will notice that something is not right. At this point she may come across Khushi making purchases for the wedding and ask her about it. Khushi will be forced to admit that she is getting married. She will also tell her that it is a small affair where only the family are invited but blurt out the venue of the marriage to La. La may mention this in her conversation to Arnav on the day of the wedding and be shocked to see that he is highly disturbed hearing this. She recollects how Khushi was in tears the day Arrnav made the announcement of his engagement to La. She finally figures out that these two are madly in love with each other and blasts him for playing with three lives. She also asks him to do something before it is too late. She gives him the address of the venue (maybe some temple) where the marriage is taking place before she leaves.
Arnav lands up at the temple around the time Shyam reaches there and Shyam gets scared seeing him. Arnav though may not notice Shyam. Before he does, Shyam escapes from there. Arnav in the mean time goes into the temple and sees a bedecked Khushi. He would hesitate coming forward because he is still battling his emotions. With the groom not turning up for the wedding, Buaji will start ranting again about the problems Khushi brings with her. Although they try to get in touch with Shyam, it will be in vain as he would have switched off his mobile. Buaji will start screaming that now Khushi will not get married as she is considered an ill omen. Shashiji will try hard to say something and in the process get seriously ill. Arnav recollects what had happened to his sister all those years back when her wedding did not materialise and decides that he will not let Khushi go through that pain. Thus, amidst all the high drama, he steps in and say that he will marry Khushi much to every one's shock. The rituals will be hastily completed and Arnav will bring her home. The rest of the family are shocked to see Khushi and Khushi is equally shocked to see Shyam who is introduced as Anjali's husband.
She corners him when alone and threatens to expose him to the family but he turns the table and instead makes it seem as though she was trying to seduce him. Anjali witnesses this and is shocked. She believes the lies that he perpetrates and tells Arnav about Khushi's true colours. Although Arnav would not believe it, he is forced to send Khushi away because he realises that it is more dangerous for Khushi to be under the same roof as Shyam. He also wants to preserve his sister's married life as he knows the truth can kill her. So he will pretend he still hates her for forcing him to get married when he did not want to and wants her out of his life. Khushi is heart broken and leaves. She decides not to go back to her own home as they will be upset knowing that her life is ruined. La may come across her and force her to stay with her till she can make up her mind what to do about her future.
Khushi will start working in another company to fend for herself. Arnav buys that company in order to be close to Khushi and also ensure that Shyam does not harm her. He does not let her know that he still cares for her though and is at his khaddoos best. Khushi may slowly break his guard and they finally unite only to be torn apart again by their past. How they come back together after this turmoil may be the rest of the story.
Edited:
I had missed out on Payal and Akaash. So I guess we can have their track included too if Khushi first decides to keep quiet about Shyam taking into account Anjali's feelings. So everything may go as if normal. Arnav may continue to remain aloof with Khushi as he is scared of giving in to his feelings lest he gets hurt as in his past. He will pretend that he is unhappy about being forced to marry her and they may stay away from each other in the bedroom but the s***l tension will be strong as each tries to keep a check on their feelings. In the meantime Mami may press for Akaash's wedding and he will refuse to marry anyone but Payal. Since Anjali already supports this and Nani may join in, Mami may be forced to accept Payal. Akaash-Payal may get married and live in Raizada house. Her parents return to Lucknow after Shashi recovers completely. Shyam in the meantime cannot keep a check on his growing desires for Khushi and may finally try to molest her. When Anjali witnesses them together he may put the blame on Khushi. The rest of the track as I had written may then follow.